1. Field of the Invention
The present invention relates generally to the field of thermal ablation where heat is delivered to necrose or ablate a diseased body organ. More specifically, the invention provides methods and devices for thermally ablating hollow body organs, such as the uterus, by heating a thermally conductive fluid disposed within the organ.
"Minimally invasive" surgical procedures have recently been developed as alternatives to conventional "open" surgery. Of particular interest to the present invention are minimally invasive surgical procedures relating to thermal treatment of hollow body organs, and particularly to treatment of the uterus. A variety of such thermal treatment procedures have been proposed which rely on a catheter to deliver heat to the interior of hollow body organs which are filled with a thermally conductive fluid. The heated fluid is then employed to heat the mucosa sufficient to induce injury and necrosis of the organ. For example, U.S. Pat. Nos. 5,045,056; 5,100,388; 5,188,602; 5,222,938, and U.S. patent application Ser. Nos. 08/073,639 and 08/266,037, the complete disclosures which are herein incorporated by reference, describe catheters having a conductive heating element disposed on the catheter which heats a thermally conductive fluid by conventional thermal conduction to a temperature sufficient to destroy the mucosa or endothelial lining of the organ, resulting in deactivation of the organ.
Although workable, the use of such catheters having conductive heating elements at their distal ends to deliver heat within the uterus can be problematic in certain respects. For instance, heat distribution through the thermally conductive fluid can be non-uniform, thereby requiring an increase in the total amount of heat delivered to the fluid in order to assure that the temperature of all portions of the mucosa are raised above the threshold level necessary to induce injury and necrosis. However, such an increase in heat delivery may raise the temperature of some portions of the mucosa above a desired maximum temperature. Such excessive heating is undesirable in that it can in some cases result in injury to adjacent organs. As an alternative, some attempts have been made to induce an oscillatory flow between a lumen in the catheter and the organ in order to reduce the temperature gradient within the fluid. Although oscillatory mixing of the thermally conductive fluid enhances heat delivery to remote locations within the organ, mixing by inducing an oscillatory flow between the catheter lumen and the organ may be undesirable in some cases because it often creates pressure waves within the organ. Such pressure waves may be particularly problematic within the uterus because hot conductive fluid may be forced through the fallopian tubes and into the abdominal cavity, thereby potentially causing damage to adjacent organs. Oscillatory mixing is also undesirable because of potential blockage of the catheter lumen by blood clots or tissue particles that may be suspended in the fluid.
Another drawback to such conductive heating catheters is the limited capacity of their conductive heating elements to rapidly deliver necessary heat to the thermally conductive fluid. In order to deliver sufficient heat to remote portions of the organ lining, it may be necessary to raise the surface temperature of the heating element above a desired maximum temperature. However, excessive heating can result in fouling of the heating element as a result of coagulation and denaturing of blood and other proteins that may be present in the fluid, thereby reducing the heat transfer capacity of the heating element and increasing operating time.
Another problem experienced when attempting to thermally ablate a hollow body organ is the existence of air bubbles that may become trapped within the organ when introducing the thermally conductive fluid. Air bubbles trapped within the organ will tend to decrease the amount of heat transfer from the fluid to the endometrium. Further, in the case of the uterus, trapped air will tend to expand when it is heated and may cause the intrauterine fluid pressure to increase above the desired maximum, resulting in potential leakage through the fallopian tubes.
Hence, for these and other reasons, it would be desirable to provide improved methods and devices which would overcome or greatly reduce these and other problems. In particular, it would be desirable to provide methods and devices having improved heat transfer characteristics so that adequate heat may rapidly be delivered to the fluid without fouling of the heating element. The methods and devices should also provide for a uniform heating of the fluid within the organ, preferably without undesirably increasing the intraorgan pressure. In one aspect, the devices will preferably be sufficiently small to allow introduction into the uterus through the cervical canal. Finally, the methods and devices should allow for the thermally conductive fluid to be introduced into the uterine cavity within a desired pressure range and so that air bubbles do not become trapped within the uterus.
2. Brief Description of the Background Art
As previously described, U.S. Pat. Nos. 5,045,056; 5,100,388; 5,188,602; and 5,222,938 describe catheters having a conductive heating element that conductively heats a thermally conductive fluid within a hollow body organ.
U.S. Pat. No. 4,676,258 describes a device for radio frequency hyperthermia having a first electrode disposed in a tract or organ and a second electrode disposed on an outer circumference of a person to heat a tumor or malignancy region deep inside the person.
U.S. Pat. No. 5,368,591 describes a balloon catheter having heating electrodes disposed within the balloon.
U.S. Pat. No. 5,257,977 describes a catheter for introducing a heated fluid into the urethra.
U.S. Pat. No. 5,242,390 describes a device for introducing a heated liquid into the uterus.
U.S. Pat. No. 5,195,965 describes a catheter having a balloon for receiving a heated liquid.
U.S. Pat. No. 5,159,925 describes a catheter for laparoscopic cholecystostomy and prostate or gall bladder oblation. The catheter includes a distensible bladder at its distal end for receiving a heated fluid.
U.S. Pat. No. 4,469,103 describes a system for applying localized infrared electromagnetic energy to an effected area of a body.
U.S. Pat. No. 5,277,201 describes an endometrial ablation apparatus having an electroconductive balloon at its distal end for extending the organ and making electrical contact with the endometrial lining to be destroyed.
U.S. Pat. No. 4,430,076 describes a uterine manipulative and injector device for uterine insertion. The device includes an inflatable member at its insertable end which may be inflated to seal the lower portion of the uterus to retain fluid or gas injected into the uterine cavity.
U.S. Pat. No. 4,375,220 describes a microwave applicator for intracavity treatment of cancer.
U.S. Pat. No. 4,979,948 describes a catheter having a capacitative balloon electrode which may be expanded by an electrolyte solution to conform and make contact with the mucosal layer.
PCT Application No. WO 81/03616 describes a microwave antenna system for intracavity insertion for inducing hyperthermia by microwave irradiation.
Christoph D. Becker et al., Long Term Occlusion of the Porcine Cystic Duct by Means of Endoluminal Radio Frequency Electrocoagulation, Radiology 1988, 167:63-68 and Christoph D. Becker et al., Gall Bladder Ablation Through Radio Logic Intervention Choela and Experimental Alternative to Cholecystectomy, Radiology 1989, 171:235-240 describe gall bladder procedures using radio frequency energy.
German Patent No. DE 4123-418-A and Soviet Union Patent No. 1319848A describe thermal urology procedures.
Daniel B. Fram et al., In Vivo Radio Frequency Thermal Balloon Angioplasty of Porcine Coronary Arteries; Histologic Effects and Safety, American Heart Journal, 1993, 126:969-978 describes a radio frequency balloon catheter having two electrodes located on the catheter shaft within a balloon lumen.
Product brochure Heads Up, Heated Balloon Catheters, Copyright 1994, describes a balloon catheter having fluid that is heated by radio frequency current flowing between electrodes disposed within the balloon.
William S. Yamanashi et al., Properties of Electromagnetic Field Focusing Probe, The Journal of Vascular Diseases, Nov. 1988, p. 953-954 describes an electromagnetic field focusing apparatus having a radio frequency generator, a solenoid coil, and a hand-held catheter probe for producing eddy currents in biological tissues.